1. Field of the Invention
The present invention relates to a method of continually forming plural copies from a single electrostatic latent image.
2. Prior Art
A method of making plural copies is known which comprises, for example, forming an electrostatic latent image on a photosensitive member, developing the latent image, transferring the developed image to paper and thereafter repeating the developing and transferring steps only for forming the second and following copies. Although having the advantage of being simple, this method has the following drawbacks. Because the electrostatic latent image once formed must be retained over a prolonged period of time, there is the need to use a photosensitive member having excellent dark decay characteristics. This limits not only the type of photosensitive members that can be used but also the number of copies which can be made continually. Even when the photosensitive member used has outstanding dark decay characteristics, there arises the necessity of varying the developing bias voltage or transfer bias voltage with an increasing number of copies in order to maintain the initial high density.
Published Unexamined Japanese Patent Application SHO No. 56-168663 discloses another method of making plural copies wherein an amorphous silicon photosensitive member is used for forming an electrostatic latent image, which is developed and then semi-fixed by heating. The photosensitive member bearing the semi-fixed image is charged, exposed to light and developed to obtain a developed image, which is subsequently transferred onto copy paper. The charging, exposing, developing and tranferring steps are thereafter repeated for making the second and following copies. With this method wherein the image formed on the photosensitive member needs to be semi-fixed, the photosensitive member must have high heat resistance, and the photosensitive member is susceptible to damage when the semi-fixed image is removed from the member after making the desired number of copies.